Telephonic exchange system and apparatus therefor



(No Model.) 12-Sheets--Sheet 1. J. 0. SHIRAS & E. A.- EKERT.

TELEPHONIG EXCHANGE SYSTEM AND APPARATUS THEREPOR.

No. 269,238. Patented Dec.A 19, 1882.

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Paten ed 1366.19.1882.

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TELEPHONIE EXCHANGE SYSTEM AND APPARATUS TEEEEEOE.

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(No Model.)

12 Sheets-Sheet 3. J. 0. SHIRAS 8v E. A. ECKERT.

TELEPHONIG EXCHANGE SYSTEM AND APPARATUS THEREPOR. No. 269,288.

Patented De0.19, 1882.

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(No Model.)` 12 Sheets-Sheet 4. J. O. SHIRAS 8v E.. A. ECKERT.

TELEPHONIG EXCHANGE SYSTEM AND APPARATUS THEREEOR.

Patented 1100.19, 1882.

N. PETERS. Phofmnmgnphn. wnhingmn. D. C.

(No Model.) 12 Sheets-Sheet 5.

J.` 0. SEIRAS & E. A. ECKERT. TELEPHONIG EXGHANGESYSTEM AND APPARATUS THEREFOR- No.. 269,238. Patented Deo. 19, 1882.

(No Model.) 12 Sheets-Sheet 6.

J. 0. SHIRAS 8. B. A. EOKBRT.

TELEPHONIG EXCHANGE SYSTEM AND APPARATUS THEREPOR. No. 269,238. Patented Dec. 19, 1882.

(No Model.) 12 Sheets-Sheet 7'. J. O. SHIRAS 8v E. A'. BCKERT.

TELEPHONIG EXCHANGE SYSTEM AND APPARATUS THBRBFOR.

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152,gjPdsented Deo. 19, 1882.

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(No Model.) 12 sheets-Sheet s.

A J.v 0. SH'IRA'S 8v E. A. ECKERT.

TELBPHONIG EXCHANGE SYSTEM AND APPARATUS THBREFOR. No. 269,238. Patented Dec.19,' 1882.

NA PETERS mxumgngm. wnlm'ngecr n.c.

(No Model.)- 12 Sheets-Sheet 9. J. -,0..SHIRAS & E. A. ECKERT.

TELEPHONIG EXCHANGE SYSTEM AND APPARATUS THEEEEOR.

No. 269,238. PatentedDeo. 19, 1882.

mmmlulmumm U (No Model.) 12 sheetssheet 1o. J. O SHIRAS & E. A. ECKERT. TELEPHONIG EXCHANGE SYSTEM ANDv APPARATUS THEEEPOR. N0..269,238.

Patented Dec.19, 1882.

N. PErtRs, muw-lahognprur. Washington. 11C.

v (N0 Model.)

12 Sheets-Sheet 11 J. O. SHIRAS 8v E. A. EOKBRT.

TELEPHONIG EXUHANGE ySYSTEM AND APPARATUS THEREPOR.

No. 269,238. Patented Dec.19, 1882.

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(No Model.) 12 Sheets-S'heet 12. J. O. SHIRAS 8v E. A. ECKEET.

TELEPHONIO EXCHANGE SYSTEM AND APPARATUS'TEEREEOR.

ML2/0 l? @www Q UNITED STATES PATENT EETCE@ JAMES O. SHIRAS AND EDIVARD A. ECKERT, OF CINCINNATI, OHIO.

TELEPHONIC EXCHANGE SYSTEM AND APPARATUS THEREFOR.

SPECIFICATION forming part of Letters Patent No. 269,238, dated December 19, 1882 Application filed October 25, 1881.

To all whom it may concern Be it known that we, JAMES O. SHIRAS and EDWARD A. ECKERT, both of Cincinnati, in the county ot' Hamilton and State of Ohio, have invented certain new and useful Improvementsin Telephone-Exchange Systems and Apparatus Therefor, of which the following is a specification.

Our invention relates to that class ot' telephone-exchange systems wherein subscribers1 drops or indicators are divided into groups, each group being placed upon an operating desk or table and under the personal care and supervision of the operator at that table. The

Jones and Gilliland apl'raratusare types of this system. 1n these, as is. well known, only a portion ot' the subscribers wires is placed on one tablesay titty-and in this case, when the operator wishes to connect one ot' these fty wires on his board with other wires on other boards, it mustbe done by means ot' dummy or transfer wires, and a ticket must be carried by a check-boy to the operator at the other table, this ticket explaining to him whatline-wire to connect and also onto what dummy-wire to connect it; or, thecheck-boyis not used, the tirst operator must, by ineansot' telephone and transfer wires, give the necessary direction to the second operator. With this explanation it will be understood that 'each operator has individual control `of titty wires only. It is also manifest that to maketheconnection with a wire on another table it requirest-hejointaction of two operators, and either the interven` tion ot'a telephone-circuit between them or the employment ot' a check-boy.

rlhe object. of our invention is to bring all the wires running into the exchange under the individual control cte-ach operator, whereby he can individually call, connect, and disconnect any and all subscribers7 wires without the intervention of the secondpperator orcheck-boy .or tickets; and it consists in the combination,

in telephone-exchanges in which subscribers drops are divided into groups and each group is placed on a separate operating-table, ot each operatlg-table with multiple groups ot' connection devices, each of said devices being in connection with a subscribers wre,veach group being integrally known and designated in the same manner as the group of drops to (No model.)

nected, each group of connection mechanisms being integrally known and designated in the same manner as the group `ot' drops to which it is connected is known and designated, with connecting plugs or cords, test-battery, callbattery, telephone and transmitter, and disconnecting-drops, whereby each operator can answer, call up, and talk to every subscriber, trunk-line and trunk-line operator, exchangeoperator, or any other person connected to the dropV in the exchange, and can connect anddisconnect each and every wire connected to a drop in the exchange; inthe combination,

in a telephone-exchange system in which Asubscribers drops are divided into groups and each group placed on a separate operating-table under the care otoue operator, ot'each subscribers wire terminal with a series ot` connection mechanisms, the trst connection mechanism of the sriesbeingusuallyplacedbeneaththesubscribers drop, the second connection mechanism on the switch-board ot' the second tablein an integral groupot' connection mechanisms designat-l ed in the same manner as the group ot' drops to which they are connected, the third connection mechanism being placed on the switchboard of the third table in an integral group ot' connection mechanisms, designated in the same manner as the connection mechanisms of the second table and the drops of the rst, and so on with all the connection devices ofthe series until the last is reached, which .is disposed of on the switch-board ot' the last table in the same manner as the previous ones were disposed of, the last connection device being part of and forming the electric circuit for the extension of the subscribers wire back to the tirst table, Where the-circuit goes through the subscribers drop to the ground; in the combination, in a telephone exchange substantially such as above explained, ot' each connection device IOO with two rigid test-rods, one rod of each pair being connected to the corresponding rod of each pair on all the other connection devices in that series, and a bridge carried by the connection-plug to close the gap between rods of a pair, whereby a test-circuit is formed to enable each operator to ascertain it' the wire is in use, and also to prevent the operator from iisingasnbscribers wire if that subscriber has called and is waiting for an answer from the operatorin charge of thedrop; in the combination, in a telephone exchange system substantially such as hereinbefore stated, of each connection mechanism on each operating-table with one or more circuit-closers on each table, each circuit-closer being in conneetion with the telephonetransmitter, test-battery and callgenerator, and disconnecting-diop, and each of which circuit-closers can be brought into electrical connection with the connection devices by means ot telephone, connecting-rods, and plugs or keys; in the combination, in a telephone exchange system in which subsciibers drops are arranged in groups, as above stated, ot' each connect-ion device with a plug, a cord, a socket-plug, and a socket, which socket is composed of several terminals insulated from each other, these terminals being connected with a telephone and transmitter, a generator for calling, a local battery t'or testing, and a disconnecting-drop; in an improved socket composed ot' several parts insulated froin each other, which parts form the terminals ot' several electric circuits-to wit, one part being a terminal ot' a grounded open circuit including in its circnita call or ringingup battery closed by a key, another part being a terminal of a grounded circuit inclndiiig the telephone and transmitter, another being a terminal ot' the circuit leading to one pole ot' a test-battery, another being a terminal ofthe circuit to one sidelot' a disconnecting-drop, an other being a terminal of the circuit leading to the other side of the disconiiectiiig-drop; in the combination, with a socket substan. tially such as the foregoing, ot' a plug having cords and terminal pins for connection with the subscribers7 and respondents wires, and havingconnecting-surt'acesiusulatedfromeach other and so arranged relative to the parts ot' the socket that connection may be made and broken, or a fresh connection made to bring another circuit into connection by turning said plug upon its axis while resting in the socket; in the combination, with a socket and plug, of a plunger normally in contact with one of Ithe conducting-surt'aces and connectingcords of the plug and normally out ot' contact with the terminal rod of al1 operator-s telephone-circuit in said socket; in the combination, with a socket and plug substantially ot' the character stated, and with the plunger whereby the terminal rod of the operators telephone-circnit is thrown into electrical contact with a conducting-surtace and connecting-cord on said plug, ot' a wire connecting two opposing surfaces of the socket and including in its circuit a disconnectingdrop, whereby when both subscriber and respondent have been connected the operator may tall; with both by depressing the plunger; in an operators table having drops and connecting-tubes for the terminals of a group ot' subscribers wires, sockets for battery and ground connections, a telephone and disconnecting-drop, and a switch-board and numbered coiinecting-tnbes connecting with all the remaining wires ot' the exchange; in combining with subscribers wires having their drops arranged in groups at separate operating-tables, switch-connections for said wires at every other operating-table, a test-circuit including the drop-connection and each switch-connection, and having its contact established at the time the drop-sliutter falls or a connection is plugged, a test-battery,and signaling mechanism, whereby a positive signal will be given in answer to a test atanyoperatorstable whenever tlie drop has fallen or the line has been plugged at another table; in a connecting-tube having in contact therewiththe terminal ofasubscriber-s wire andthe terminal ot` a wire leading to the switch or subscribers connections on the other tables, and provided with a spring break or bridge, which normally keeps said terminals in electrical contact with each other; in a connecting-tube having combined therewith insulated test rods or posts, a subscribers wire, a circuit-wire leading to'switch or subscribers connections on the remaining tables of the series, then by return-wire to the table from which it starts, and through the drop to the ground and normally in contact with the subscribers wire, and wires leading from the test-rods to corresponding test-rods on the connecting-tubes ot' the other table of the exchange; in the combination, with a connecting-tube having insulated test rods `or posts separately connected to corresponding test-rods ot' other connecting-tubes, and also having a snbscribers wire insulated from said test-rods, ot'a circuit in normal contact with said subscribers wire and connecting it to a tube upon every other table in the exchange, and a connecting plug or pin adapted upon being inserted to throw said subscribers wire out ot' contact with the table-wire and into contact with the connecting-cord, and at the same time to throw the testposts into contact with each other and establish a test-circuit; in so combining the test-posts of the connecting-tube with the drop-shutter of the subscribers terminal that said shutter, when it falls to indicate a call, rests uponr and throws the posts into contact one witl another to establish, a test-circuit, whereby operators at any oth`er table may inform themselves that such aline has called and is for the time being blocked; in combining with the connectingtube and its test-posts a connecting-rod bearing an elastically-seated Vinsulatedl conducting-disk which comes in contact with the testposts and throws them into electrical connection as the rod is inserted into the tube; in combining with the IOO IIO

IIS

connecting-tube and its testposts a connecting-rod bearing an elast-ically-seated insulated conducting-disk which forms the contact between the test-posts, and means whereby the length of said rod may be adjusted to compensate for diderent lengths oftnbe; in combining with the connecting-tube and its test-posts a.v

connecting-rod bearing an elastically-seated insulated conducting-disk which forms the contact between the test-posts, and means whereby the force ot' said spring may be adjusted to increase the effectiveness ot' the contact between the disk and posts; and in the various other combinations and details of construction hereinafter described and claimed.

ln the drawings, Figure 1 is a perspective view of an operator-s table embodying features ot' our invention.

ber ot' tables; Fig.3, a diagram including two tables to explain the course ot' subscribers litres through the tables to their distantstations and ground-connections; Fig'. 4, a ldiagram to explain the course of the subscribers wires and the circuit through a series of tables; Fig. 5, a diagram showing two lines terminating on different tables connected to each other, and also the means for connecting and disconnecting; Fig. 6, a diagram illustrating subscribers circuit and test-circuit through three tables, with the test-circuit in action; Fig. 7, a plan view of the table-plug socket with its connections; Fig. 8, a side elevation of the sanne with the connecting-wires omitted; Fig. 9, a perspective view ot the socket-plug with connect-Y ing-cords and terminal connecting-rods; Fig.'

10, a skeleton view ot' the metallic parts of said socket-plug; Fig. 11, a vertical section through the socket and its plug, showing how the two are brought into connection, and also how a telephone is brought into circuit for talking; Fig. 12, a modification ofthe socket-plug; Fig. 13, a bottom plan view of the connecting-tube and its test-posts, partly in section to show the mode of mounting it in frame-work; Fig. 14, a Vertical longitudinal section through the same; Fig. 15, a perspective view ota connecting-plug adapted to operate with such connecting-tube; Fig.16,alongitudinalsection through said plug and its handle; Fig. 17, a detail view of a part of said plug; Fig. 1S, theconnecting-plug inserted into the connecting-tube, so as to throw the test-posts into electrical contact anddisconnect the subscribers wire from the circuit-wire going to the table; Fig'. 19, an elevation ofthe drop-shutter in its proper relation to the connecting-tube; Fig. 20, a detail showing how the subscribers drop shutter throws the test-posts into electrical contact by its fall; Fig. 21, a diagram showing the circuit established when the drop-shutter has been allowed to fall upon the test-posts by a.

snbscribers call and another post in the line 1s touched by any operator; Fig. W a dia- Fig. 2 is a diagram includgram including` various mechanisms, and representing the course of the current when the open electrical circuit for the purpose of test- The operators table in our system is provided, as usual, with a telephone, A, a transmitter, B, a treadle or crank, C, for operating the generator or magneto-electric machine which rings the distant subseribers bell. Instead of this-generator, however, a voltaic battery may be used.

At the lower part ot' the upright portion-or. board of the voperator-s table are arranged a series ot' drops, D, corresponding to subscribers terminals-say tit'ty in number, or thereabout-as usual in eXcha-i'iges,and beneath each drop a connecting-tube for that subscriber. which connecting-tube and its accessories and contacts will be hereinafter fully described. The drops ofthe tirst table ot' the series, Where the number is that above proposed, will be ,numbered from 1 to 5t), which number will also therewith on the desk portion ot' the operators table, and, for convenience and com pactness, along the angle-formed by the desk portion with the board, are arranged a series of' sockets, E, which in practice may be about one-fifth in number of the drops. These sockets receive the plug by which the connectlon is made between the subscriber and the callbattery and operators telephone, and also between the subscriber and the respondent, and their construction, as well as that ofthe plug which they receive, will be fully described at the proper time.

A disconnecting-drop, D D, is provided for each socket, and these last-named drops will be advisably arranged at the lower angle o the board, immediately behind the sockets and beneath the subscribers drops.

Upon the board, above the space devoted to the drops, are arrangedin compact form a scries ot' numbered connecting-tubes, F, in the aggregate and in their designating numbers corresponding to the drops ot' all the other operators7 tables in the exchange-that is, supposing them to be arranged on the trst table, the drops of which are numbered from 1 to 50, tle connecting-tubes ot' this upper portion, which is properly the switch-board, will be numbered from 51 to 100 for the second table, from 101 to 15() for the third table, and so on, while on the second table, the drops ot' which are numbered from 51 to 100, the connecting IOO IOS`

. as found advisable.

tubes on the switch-board will be numbered set-screw, whereby the wire may be `jammed from 1 to 50 for the iirst table, from 101 to 150 for the third table, and soon, the connectingtubes beneath the subscribers drop on each table supplying the missing numbers on the switch-board. These connecting-tubes on the switch-board we prefer to arrange in groups corresponding tothe group ot' subscribers terminals with which they are connected, those for each operator-s table by themselves, as shown, and these groups may be identified with their respectivetableseither bycolorsor bynumbers, A subscribers wire tirst comes to his connecting-tube beneath the drop on the table to which he is allotted, passes from that by means ot' a brealbconnection to the eorrespondingly-numbered connecting-tubes on the switch-board of the next table, thence trom that to the correspondinglynumbered tubes on the switch-board ot' the third table, and so on through the series until it reaches the last, when it returns to his drop. This arrangement is clearly shown in the third figure ot' the drawings. Two test-circuit wires, insulated from each other, also run from the connecting-tube beneath, each subscribers drop through his switch-connections on the switch-boards ofthe other tables, one of these test-circuit wires being in connectionwith a wire or circuit passing through a test-battery and a test-bell or signaling device on each table to the series of sockets on said tables, the other wire having its ends free or disconnected, these test-circuit wires being insulated from the subscribers circuit, and being bridged and consequently partially closed, ready for testing by his call, or in the act ot' plugging his connecting-tube or any ot' his switch-connections. In our system We work trunk-lines which connect branch exchanges in the same manner as subscribers wires-that is, we treat these lines as subscribers wires andi-un them to a connecting-tube beneath a drop on the operator-s table, which may be a table devoted to trunk-lines, (or they may ter- .minate indiscriminately in the various tables,)

giving each trunk-line' wire its appropriate number, then, by circuit-wires, runningthem to switch-boards on every other operators table in the exchange, and providing them in like manner' with test-circuits. Theret'ore each operator can test, call up, connect, or disconnect any trunk-line. These have heretofore been hard to handle, but by this system are made quite as easy as subscribers lines.

Fora proper understanding of the line ot' the current, we will now proceed to describe the connectingtubes which we have invented, and which, or some equivalent thereot', will be found necessary in the working ot' our system. F is the tubeproper,composed of metal and open at one end,at the other end being closed by someinsulating material (L -such as vulcanite-\vhich receives atits outer end a metallic head, a', screw-threaded or otherwise secured thereto. This head is perforated to receive the terminal of a wire, and is provided with a down into perfect electrical contact therewith.

At a short distance from the open end of the tube is a cross-piece or block, b, fast thereto, and having at one end a perforation, b', to receive the terminal of the subscribers wire, and a set-screw to insure its electrical contact. The wings of this block are also perforated parallel with the tube, and the perforar-tions are lined with insulating material b2 to receive the test-posts c c, which extend out beyond the open end ot the tube. These test-posts are or may be headed at their exposed ends. At their other ends they are screw-threaded to receivethecapornutd,wherebytheyaresecured to the tube at'ter having beenpassed through their bearings, and whereby also they are made to serve as astrong and efficient means otsecuring the connecti ng-tube in theframework ot' the table. For the latter purpose they are passed through the strips cl ofthe frame-work,\vhich is suitably' perforated, and alsoA has a central aperture or socket to receive the end of the tube, then through their bearings, and have their caps or nuts applied, so that the bar is clamped between their heads and the outer face ofthe cross'piece b upon the tube. This mode of securing is much more tirm and secure than would be the use ofordinary screws, and, besides, give-s an economy of parts, as the testposts are made to serve dual functions. The nuts or caps ot' the test-posts are each perforated to receive the terminal of a wire, and provided with a set-screw to hind it in electrical contact.

Upon the cross-piece b is secured a spring, e, which extends therefrom to contact with the head a', bridging the insulating or non-cou ducting material between the tube and said head; and to insure perfect electrical contact the head may be flattened on the point where the spring touches it. Aboutmidway between the ends ot' the spring it is provided with a lug, e', which takes into a slot in the1 tube, so as to project beyond its inner walls. `While the spring is down and in contact with the head a it is evident that the terminal of the subscribers wire bound to the cross-piece b will be electrically connected with the terminal of the wire bound tosaid head; but if the spring is raised this connection will be broken. The wires attached to the test-posts will be permanently out ofconneetion with either of these last-mentioned terminals. For the purpose of operating this connecting-tube, we employ a plug, G, which forms a terminal point of one of the connecting-cords usual in exchanges. This plug is composed primarily of a metabic rod, pin, or spindle, f, which tits easily into the tube, and its forward end is beveled, as at j', and at a slight distance behind the bevel has a notch,j". At its rear endit is provided with an insulating-handle, G', and is in electrical contact with the end of the connecting cord f3. Vhen it is introduced into the tube its beveled end will push up the lug e upon spring e and break the contact between that I oo ISO

spring and the head a' of the tube, and when it has been pushed home thelug upon the spring will drop into the notch f2 and hold it fast, the notch, however, being so shallow that the spring is still kept from contact with the head a', and the connection between that and the subscribers wire remains broken. To disengage the spindle from the socket it need only be turned upon its axis until the lug has ridden up its periphery out of the notch, when it can readily be withdrawn.

Upon the shank ot' the spindle is a disk, g, which on its forward side is stopped by a shoulder ou the spindle, and on the rear side is seated against a coiled spring, g', received in a suitable socket in the handle. The main portion of this disk, and that part ot' it in contact with the spindle, is composed of insulating material, and on its face it is provided with a metallic annular or equivalent conduct-ingerirt'ace, g2, which surface, when the spindle is forced down into theconnectng-tube, is pressed by the spring against the heads of the testposts, so as to bring them into electrical conltact with each other.

We prefer to construct the handle in such a manner as to allow of the adjustment of the spindle as to length, and also to permit ot' the ready removal ot' the connecting-cord and its replacement by another in case this is desirable. To this end We form the handle with a n socket portion, h, which has a cylindrical recess to receive the coil-spring, and at its rear end is closed and has a central screw-threaded aperture, into which the screw-threaded rear end of the spindle is inserted to a greater or less extent, as may be desired. That portion of the spindle projecting rearwardly from the socket-piece takes into and holds one end of the double nut h', which beyond this has an enlarged screw-threaded socket to receive the cap piece t'. The connecting-cord f3 passes centrally through an aperture in this cap-piece, and at its inner end is hunched or bent down, so as to prevent escape. The periphery ofthe cap-piece is covered by an insulating-sleeve, t", in case the cap-piece itself' is not made of insulating material. This sleeve will be secured by screw-thread or otherwise, as shown. A loose sleeve, h2, is also provided to go over the double nuth', and when the cap-piece is screwed into position it will hold the sleeve in place, and will also jam the exposed ends ofthe connecting-cord into electrical contact with the spindle orplug-rod.

As already stated, one of the connectingtubes just described is placed under each subscribeis drop on each operators table, and is known by the number given to said drop; and above the space alloted to these drops, in What we term the switch-board, other similar connecting-tubes are arranged in compact order and numbered individually to correspond with the subscribers7 drops on every other table in thc exchange, so that if there are tive hund red subscribers, and tift-y to a table, there will be tlt'ty tubes beneath the drops on one table and four hundred and titty tubes upon the switch-board of that table. Taking the first table for illustration, and the wire lc leading to subscriber No. 5, (see Fig. 6,) this wire has itsterminal in the aperture b in the crosspiece b of the connecting-tube beneathhis numbered drop, and by means ot' the breakspring is normally in electrical contact with the circuit-wire k', attached to the head in this connecting-tube, and wire 7s' runs to the crosspiece b of connecting-tube No. 5 on the switchboard ot the second table, thence, by means ofitbe'break-spring and head-piece a ot' that connecting-tube, connects with wire 7a2, which runs to the cross-piece ot' con meeting-tube No. 5

on the switch-board of table No. 3. and, reachintermediate switch-connections will at once be cut out of circuit, and at the same time, by means of the disk on the plug, the test-circuit will be partially established. This latter circuit is composed as follows: From test-post c upon, for example, this subscribers drop, No. 5, a Wire, Z, leads successively to each corresponding testpost ot the connecting-tubes similar iu number on the switch-boards ot' the other tables of the series, and from the testpost c' of the connecting -tube on the last switch-board a wire, l', returns successively to each test-post c otj the series until it reaches the test-post c of the rst connecting-tube. This last wire, l', has a contact with a local or test battery, L B, the opposite pole ot' this battery being electrically connected by a wire, 12,

with a test-bell, T B, or buzzer, or drop, or

signal device, whichever is used on each table, each test-bell being in electrical contact with a terminal in every plug-socket upon its table. An operator at the third or any other table may now complete the test-circuit by plugging a socket and touching the head ot' the test-poste with the terminal ot' connectingcord ou said socket-plug, and the bell or signal device, being actuated by the current, will at once give notice that the line is in use; but should it not be in use there will be no testcircnit, no current, and no signal from his bell, and he may at once proceed to call the line.

Vhen a subscriber calls it often happens that thcoperatoris engaged in answering other calls.l There will therefore be an interval after his call during which his connecting-tube will remain unplugged. In order to establish the test-circuit during this interval to prevent any other operator interfering with the line, we arrange the drop and connectingtube in such relation to eachother that when the drop-shutter falls to announce a call it strikes and rests against the heads of the test-posts and brings them into electrical contact with cach other, remaining down until the operator is ready to IIO plug the tube, so that from the moment of the call a signal w'ill be given in answer to any test.

An efficient means of insuring electrical contact between the drop-shutter D and the heads of the test-posts is shown in Fig. 20. Upon the shutter is secured a curved spring, m, and projecting upwardly from each testpost is a wire, m', into such position that when the shutter falls the ends of its spring will rest upon and electrically connect the two wires, being firmly pressed against them by the leverage ot' the shutter.

The plug-socket E is composed of several terminals insulated from each other. The

"form which we have shown has four terminals,

numbered respectively l, 2, 3, and 4, sub-- stantially as shown in Figs. 7, 8, and 1l, each terminal being a metallic strip segmental in cross-section, so that the socket may be cylndrical and attached at its hase to the non-conducting block Z3, by which its insulation is maintained. Each metallic strip or terminal is, for perfect contact, provided with a spring,

and thewireitisinelectrical contactthrough a telephone and transmitter to the ground. The terminal l of the socket is connected by a wire with the test-bell and test or local battery, the other pole of which, as above stated, is connected with a wire, Z', of the test-rods c. The terminals 2 and 4 are connected with the operators disconnecting-d rop D D by independent wires, and establish a circuit to that drop, and the terminal 3 is connected by a wire through call-battery key with the callrbattery O B, and thence to the ground.

The socket-plug E is composed of a body, 0, ot' insulating material, and bears two separate conducting-surfaces, o o2, supported thereon, each ot' which has a bindingscrew to receive the terminal of a conducting-cord, f3, provided at its end with a connecting-plugsuch, for instance, as above described. The conducting-surface o is in electrical contact with a plunger, 03, which passes centrally through the rod, and is spring-seated, so that it may he normally in an elevated position. This electrical contact between the surface and plunger may be either by means of a flexible wire between the two or else a rubbing contact, as in the modification shown in Fig. 12. rllhe plunger, if depressed while the socketplug is in the proper position, will come in contact with the telephone-rod and connect the telephone through the connecting-cord and connecting-plug with a wire to a distant station, so that the operator may talk to the subscriber or respondent at that. station. ,3y

turning the plug axially its conducting-surfaces o o2 may be brought into contact with the terminals l and?) or 2 and 4 of the socket, so as to bring into or throw out ot' action the test-battery and test-bell through terminal l, the call-battery through terminal 3, or the disconnecting-drop through terminals 2 and 4, these all being, in addition to the telephonecireuit, established by the depression of the plunger.

The construction of the plug-socket and the connection given its terminals enable us to tap or milk the wiresthat is, to talk to both subscriber and respondent at the same time. As the plunger is, in rubbing or otherwise, in electrical contact with the conducting-surface o of the socket-plug, and therefore with the binding-post thereon, whenever the plug is so placed as to bring this conducting-surface in contact with socket terminal l and the opposite conducting-surface, o2, in contact wi th socket terminals 3,-and the connecting-plugs are inserted one in the callers tube and the other in the respondents, it will follow, upon the depression ot' the plunger into contact with the telephone terminal, that the current will ow from the telephone A and microphone B, by their permanent wire, through telephone terminal as and plunger o, thence to the conductingsuri'aces o', where it splits, one portion going by Way of the immediate connectingeord, connecting-plug, and tube to one of the parties at his distant station, and the other, by conducting-surface o', to socket terminal 1, thence by wire to disconnecting-drop and socket-terminal 3, conducting-surface o", and the second connecting-cord, coimecting-plug, and tube to the remaining party, thus enabling each party to hear what the operator is saying to the other.

Besides the mechanism already mentioned, the operators table is further provided with an answer-drop, A D, one terminal ot' which is grounded and the other connected to the back contact, 1), of the call-battery key K, so that wlren said key is released after a call and returns to its normal position of rest the terminal 3 of the plug-socket will be in circuit with the answer-drop and the latter will be actuated by the response ot the party called.

The operation ot' our invention is as follows: Supposing Smith wishes to talk t-oJones, Smith rings his bell, which causes the annunciator on the operatoris tablesay table No. l-to drop. It" the, operator at table No. l has some other calls to attend to and keeps Smith waiting, no other operator-will call for Smith, as the shutter on his drop has by its fall partially closed 'the test-circuit, so that all the other operators,

upon testing, will be informed that the line is occupied, and will not interfere. The course of the testcircuit in this case, should any operator test while the shutter ot` Smiths drop is down, is indicated in Figs. 6 and 21, the arrows dying with the low of the current-` that is, the course is from the battery, past the intermediate series ot' test-posts c', to the post beneath the subscribexs drop, then through IOO IlO

I the shutter to the opposite testpost, c, and back through the. several switch-boards to the testing-contact, thence through connecting-cord to the plug-socket terminal l ou the table of the operator testing, and hy test-bell to battery. The test-rods of Suiiths line at table No. l are directly beneath his drop. His test-rods on all iheother tables are placed on the switch-boards of those tables. The operator at table No. l now having time to aliswerSmiths call, does` so, rst by putting back the sllutter of the drop, theil iliserting the connecting-cord plug-say that one ill contact with conducting-surface o/ iiito the tube directly beneath Smitlis drop, then placing the socket-plug into the socket E, Fig. 22, ill such manner as to bring the terminal 3 of the ringing or call battery iii electri cal contact with the connecting-cord aiid the connectingplug which he inserted into Smiths connecting-tube. Having done this, he depresses the call-battery key K, and the cllrrent goes out onto Siiiiihs wire and rings Smiths bell iii his otce, announcing to Smith that his call was received. The insertion of the plug into .the connecting-tube raises the breakspring out of the hack contact, a', which prevents tlie call current from flowing toward other tables. The operator, having answered Smith hy ringing his bell, throws on the tele! phone, alid, by talking, ascertains his wants. To do this lie gives the plug-socket a quarterturii, which breaks the connection between its conducting-surface o alid the terminal 3 of the socket, throwing out the call-battery alid answer-drop circuit and bringing the conductingsurfaces o and o2 ilito contact with terminals 2 and 4 of the socket, which terminals, by connecting-wires, torni a partial circuit including the disconnectingdrop, then depresses the plunger ot' the socketplug until it touches the end ot' the telephone rod or terminal. The conducting-surface 0 of the socket-plug is in rubbing or other contact with the plunger. Hence only the current in contact with the pluliger will flow onto thiscondacting-surface, and thence to the connecting-cord. The plunger heilig brought into contact with the telephonerod completes theteleplione-circuit from the ground in the exchange to Smiths distant station by thc following route: from ground by microphone to telephone, to the 'telephone-rod, hy contact onto the plunger, by rubbing or wire contact onto the conducting-surface of the socket-plugand the connecting-cord, to the conheating-plug, to Siniths connecting-tube, onto the brass shoulder or cross-piece used in attaching' said tube to the ol'ierating-table,finally by wire to Smiths office, aiid then to the ground. The operator, having talked with Smith, finds that he, wishes to coiiiinniiicate with Jones. He then tests Joness line to see it' it is in use, and does this with the other connecting-rod by touching with the plug the lower testpost, or, if the two test-posts are in horizontal position, then the left-hand post, first, however, turning back the socket-plug to brilig its conducting-surfaces in contact with erator tells Smith that Joness lille is in use.

It', however, no signal is given, the operator inserts the second connecting-cord plug ilito Joness connecting-tube, the rst plug remaining all this time in Smitlis connecting-tube. Now, ifJonesstlropisoii operating-table No.1, his connectingtube wll` be found directly be` ncath his drop; butif his drop is on some other table-say table No. S-the connecting-tube which the operator in this case m ust use will be found on theI switch-board portion oftableNo. 1, alid Joness tube will be found in that group of tubes coiiliected with drops of table No. 3, and will be identified by a number corresponding with Joness number o'ii that table. Then the operator depresses the call-battery key, when vthe current Hows out onto Joness line and rings the bell in his office. Jolies, hearing the bell, replies by turning his crank. The. current flows to theexcliange and operates the answerdrop on the operatoi-s table, as the call-battery key, on being released, has sprung back into its normal position, resting lipoll back contact, p, which connects by permanent wire with the answer-drop, as iii Fig. 22. The coilducting-surf'ace o2 of the socket-plug being now in contact with the terminal 3 of the socket, it might be supposed that the test-battery would ili some manner disturb Smith either at the time of testing Joliess lille or when calling him, since Smiths liiie would be connected with the test-battery by means of terminal l of tliesocket aiid conductiiig-surfaceoofthe socket-plug alid connecting-cord; but the test-battery works oil a strictly metallic circuit, and has no grou:id-connections. So, although one pole of the battery is in this case thrown on Smiths line, ilo current will tlow,as there is iio path to complete. the circuit to the other pole ot' the battery, the test-rods heilig insulated from the lille-wire of Smith and all other linewires. Jolies having answered, the operator again turns the socket-plug, brings its conducting-surfaces ilito contact with the terminals 2 and 4, depresses the plunger, and by telephone informs Jolies that Smith wishes to talk with him. As terminals 2 alid 4 ofthe socket are both connected with each other by means of a wire passing from one tothe other, aiid iii its path traversing an electro-magilet that forms the disconnecting-drop, it' any current is now thrown onto Joness liiie by means of the terminal 2 ot' the socket the same current will split at said terminal and a portion flow onto the wire, running through the disconnectilig-drop to terminal 4, thence by conducting-surface of the socket-plug to'Siniths socket-cord. Therefore when the operator ailnounces to Jones that Smith wishes to talk with him, Smit-h as well as Jolies hears the announcement. The two parties are now coilnected together under the following coliditions: (a) they cannot be interfered with, as

testing will prevent that; (b) both Joness and Smiths drops are cut out ot' circuit by the insertion ot' their connecting-plugs, so that when either rings ott' there is no danger of his drop,

being actuated; (c) the disconnecting-drop is in circuit, which will Iannounce to the operator when to disconnect them. The parties having rung ott', the plugs are withdrawn and cords allowed to hang down loose.

Having thus described our invention, we would state that the principle of our improved exchange system is not contined to the precise mechanism herein described, since, for instance. we ina)1 substitute for the circuitwire extending from the subscribers7 terminals through the series ot' switch-connections an open electrical circuit extending from theline side of the subsrribens drop to the switchboard ofthe other operating-tables, as in Fig. 23, employing suitable means for switching the ground-wire ot't' ot' the connection with subscribers and circuit wires', leaving the two latter still connected, so that an operator, by plugging the switch-connection, may cause the subscribers drop to t'all as if the subscriber himselt` had called, thus notifying the operator at that subseribers table, who, upon ascertaining the source of the call, will proceed to break the ground-connection. The specific arrangement and mechanical devices employed in this moditication may hereafter be made the subject ot' a separate application.

We claiml. The combination, in a telephone-exchange system in which subscribers7 drops are divided into groups, each group upon a separate operating-table, of each operating-table with multiple groups ot" connection devices, each of said devices being in permanent connection with a subscribers wire, each group being known and designated in the saine manner as the group of drops to which its connection devices are connected.

2. The combination, in a telephone-exchange system iu which subscribers drops are divided into groups, each group upon a separate operating-table, of multiple groups ot' connection devices upon each table, each ot' said devices being in connection with a subscriber-s wire, each group being integrally known and designated in such manner as to identifyT it with the table bearing the group of subscribers wires to which it is connected, and each individual connecting device being known and designated by the number, sign, or mark which identifies the individual subscriber with whose wire it is connected.

3. The combination,in atelephone-exchange system, with subscribers7 drops, trunk-line drops, and employes7 and officers drops divided into groups, and each group placed upon a separate operating-table under the care of one operator, ot' multiple groups of connection mechanism on each table, each group being connected with a separate group of drops,

so that all the drops in the exchange are thus connected, each group Pof connection mechanism being integrally known and designated in the same manner as the group ot drops to which it is connected is known and designated, connecting plugs and cords, test-battery and call-battery, telephone and transmitter, and disconnecting-drups, whereby each operator can answer, call up, and talk to every subscriber, trun k-line, and trunk-line operator.

4. The combination, in atelephoneexchange system in which subscribersdrops are divided into groups and each group placed on a separate operating-table under the care ot' one opcrater. of each snbscribetis wire terminal with a series of connection mechanisms, the first connection mechanism ofthe series being usually placed beneath the subscribers drop, the second connection mechanism on the switchboard ot' the second table in a dened group ot' connection mechanisms designated in the same manner as the group of drops to which they are connected, the third connection mechanism being placed on the switchboard ofthe third table in a defined group of connection mechanisms designated in the same manner as the connection mechanisms otl the second table and the drops ot' the tirst, and so on with all the connection devices ot' the series until the last is reached. which is disposed ot' on the switch-board ot' the last table in the same manner as the previous ones were disposed of, the last connection device being part and forming the electric circuit for the extension of the subscriber-s wire back to the rst table, where the circuit goes through the subscriber-s drop to the ground.

5. The combination, in a telephone-exchange system substantially such as above explained, of each connection device with two rigid testrods, one rod ot' each pair being connected to IOO IOS

the corresponding rod ot' each pair on all the other connection devices in that series, and a bridge carried by the connection-plug to close the gap between the rods ot a pair, whereby a test-circuit is t'ormed to enable each operator to ascertain it' the wire is in use, and also to prevent the operator from using asubscribers wire it that subscriber has called and is waiting l'or an answer from the operator in charge ot' the drop.

6. The com bination, in a telephoneexchange system substantially such as hereinbefore stated, of each connection mechanism on each operating-table with one or more circuit-closers on each table, cach circuit-closer being in connection with the telephone, transmitter, test-battery, call-generator, and disconnectingdrop, and each ot' which circuit-closers can be brought into electrical connection with the connection devices by means of telephone-connecting cords and plugs or keys.

7. The combination, in a telephone-exchange system in which subscribers drops are arranged in groups, as above stated, of each connection device with a plug, a cord, a socketplug, and a socket, which socket is composed ot' several terminals insulated from each other,

these terminals being connected with a tele- IIS 

